Boron-Salphen Conjugate based Molecular Probe Exhibiting Fluorescence On-Off-On Response in Detection of Cu²⁺ and ATP...

Synthesis and photophysical properties of a fluorescent probe HBD is described. Probe upon interaction with metal ions, anions and nucleoside pyrophosphates (NPPs) showed fluorescence quenching with Cu²⁺ due to chelation enhanced quenching effect (CHEQ). Moreover, interaction of ensemble HBD.Cu²⁺ with anions and NPPs showed fluorescence "turn-On" response with ATP selectively. "On-Off-On" responses observed with Cu²⁺ and ATP is attributed to an interplay between ESIPT and TICT processes. Cyclic voltammogram of probe exhibited quasi-reversible redox behaviour with three oxidation and two reduction potentials and the change in band gaps of probe suggested the interaction with Cu²⁺ and ATP. The 2 : 1 and 1 : 1 binding stoichiometry for an interaction between probe and Cu²⁺ (LOD, 62 nM) and ensemble, HBD.Cu²⁺ with ATP (LOD, 0.4 μM) respectively are realised by Job's plot and HRMS data. Cell imaging studies carried out to detect Cu²⁺ and ATP in HeLa cells. Also, the output emission observed with Cu²⁺ and ATP is utilized to construct an implication (IMP) logic gate. Test paper strips showed naked-eye visible color responses to detect Cu²⁺ and ATP. In real water samples probe successfully detected copper (0.03 μM) between 5-6.5 ppb level (ICP-MS method).